Most all aircraft have various actuation systems used to operate doors, control surfaces and the like, such as a control flap on a wing. Such actuation systems may have a variable displacement hydromechanical drive means, such as a hydromechanical motor which uses a variable swashplate or wobbler plate which varies the piston displacement of the motor. Heretofore, a single stage flow regulating valve typically was used to control motor speed, but such valves allow the motor to overspeed and/or oscillate when subjected to aiding loads. To control overspeed and/or oscillation due to any aiding loads, mechanical provisions have been used to lock the swashplate in some fixed displacement position. The drawback to such mechanical means is that additional hardware must be provided for latching the swashplate.
In aerospace applications, weight and packaging parameters are quite critical. Whenever any mechanical means, such as locking devices, must be added in any system of the craft, additional weight and packaging requirements necessarily result.
This invention is directed to solving the problem of controlling overspeed or other undesirable characteristics of a motor in a variable displacement hydromechanical actuation system without additional mechanical hardware in order to maintain low weight and size parameters for the system. This is accomplished by a compact multi-stage flow regulating valve which controls motor speed for opposing, no-load and aiding load conditions to obviate mechanical latching or other such control means for the motor.